Stalling at low idle, runs strong with lots of throttle

dtag31

Recruit
Joined
Jul 15, 2019
Messages
3
Hi Everyone,
Running a 92 Mariner 25hp on a 15ft aluminum boat. I get to the dock, lift the fast idle lever, pull the choke, and she starts right up. Over the next minute I will push back in the choke and slowly lower the high idle lever as the boat warms up, until I can fully close it after about 60 seconds and take off for the day... no concerns there.

My worry, after I drive to a spot and fish, if the motor sits for more than 30 minutes, I need to go through this entire procedure again. Even worse, it is getting harder to get it into gear without the motor stalling. I will lower the fast idle lever and need to quickly give it some heavy throttle. Sometimes it will bog, barely move, then take off at full force like nothing was ever wrong. Other times it will just choke and die.

A few side notes, I rebuilt the carb this winter and everything ran fine first thing this spring. I used to be able to let the motor sit for hours, and fire right back up without the fast idle lever. This season has been a slow degradation in performance (more often I need high idle and need to warm it for longer and longer). Also, when starting there is a tiny amount of white smoke that dissipates within 3 seconds (not sure if this is normal).

This is my first boat, and while I am handy, I have never worked on motors before, so please bear with me. I have been fishing 2 times a week and now feel like I am out of commission, I don't want to do possible harm to the motor.

Thank you so much,
Dillon
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
39,259
Have you done a compression test.------Part of proper maintenance is a new impeller every 5 years or so.-----Have you looked / installed a new one ??----Tried opening the low speed mixture needle 1/2 turn , yes or no ?
 

dtag31

Recruit
Joined
Jul 15, 2019
Messages
3
No to all of the above, bought the boat used this winter and I suspect none of the above was done. Which screw is the low speed mixture?
 

dtag31

Recruit
Joined
Jul 15, 2019
Messages
3
I ordered a new impeller repair kit to swap everything out, but the cooling water stream coming out of the engine seems to be strong. Seems more like a fuel delivery issue, but I can't figure out why it is struggling at idle/low throttle, then suddenly not having an issue if I can get it to high throttle
 
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